The validity of psychiatric diagnoses: The case of 'specific' developmental disorders

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Author(s)
Dyck, Murray
Piek, Jan P.
Patrick, Jeff
Griffith University Author(s)
Year published
2011
Metadata
Show full item recordAbstract
We tested whether developmental coordination disorder (DCD) and mixed receptive expressive language disorder (RELD) are valid diagnoses by assessing whether they are separated from each other, from other childhood disorders, and from normality by natural boundaries termed zones of rarity. Standardized measures of intelligence, language, motor skills, social cognition, and executive functioning were administered to children with DCD (n = 22), RELD (n = 30), autistic disorder (n = 30), mental retardation (n = 24), attention deficit/hyperactivity disorder (n = 53) and to a representative sample of children (n = 449). Discriminant ...
View more >We tested whether developmental coordination disorder (DCD) and mixed receptive expressive language disorder (RELD) are valid diagnoses by assessing whether they are separated from each other, from other childhood disorders, and from normality by natural boundaries termed zones of rarity. Standardized measures of intelligence, language, motor skills, social cognition, and executive functioning were administered to children with DCD (n = 22), RELD (n = 30), autistic disorder (n = 30), mental retardation (n = 24), attention deficit/hyperactivity disorder (n = 53) and to a representative sample of children (n = 449). Discriminant function scores were used to test whether there were zones of rarity between the DCD, RELD, and other groups. DCD and RELD were reliably distinguishable only from the mental retardation group. Cluster and latent class analyses both resulted in only two clusters or classes being identified, one consisting mainly of typical children and the other of children with a disorder. Fifty percent of children in the DCD group and 20% in the RELD group were clustered with typical children. There was no evidence of zones of rarity between disorders. Rather, with the exception of mental retardation, the results imply there are no natural boundaries between disorders or between disorders and normality.
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View more >We tested whether developmental coordination disorder (DCD) and mixed receptive expressive language disorder (RELD) are valid diagnoses by assessing whether they are separated from each other, from other childhood disorders, and from normality by natural boundaries termed zones of rarity. Standardized measures of intelligence, language, motor skills, social cognition, and executive functioning were administered to children with DCD (n = 22), RELD (n = 30), autistic disorder (n = 30), mental retardation (n = 24), attention deficit/hyperactivity disorder (n = 53) and to a representative sample of children (n = 449). Discriminant function scores were used to test whether there were zones of rarity between the DCD, RELD, and other groups. DCD and RELD were reliably distinguishable only from the mental retardation group. Cluster and latent class analyses both resulted in only two clusters or classes being identified, one consisting mainly of typical children and the other of children with a disorder. Fifty percent of children in the DCD group and 20% in the RELD group were clustered with typical children. There was no evidence of zones of rarity between disorders. Rather, with the exception of mental retardation, the results imply there are no natural boundaries between disorders or between disorders and normality.
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Journal Title
Research in Developmental Disabilities
Volume
32
Issue
6
Copyright Statement
© 2011 Elsevier. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.
Subject
Health, Clinical and Counselling Psychology
Public Health and Health Services
Specialist Studies in Education
Psychology